According to the boards' consistent case law, the guiding principle is that deleting meanings of residues in a generic chemical formula must not lead to the selection, in the respective lists, of a particular combination of single, specific but originally undisclosed meanings of residues (see T 615/95 and T 859/94).
In T 615/95 there were three independent lists of sizeable length specifying distinct meanings for three residues in a generic chemical formula in a claim. One originally disclosed meaning was deleted from each of the three independent lists. The board stated that the present deletions did not result in singling out a particular combination of specific meanings, i.e. any hitherto not specifically mentioned individual compound or group of compounds, but maintained the remaining subject‑matter as a generic group of compounds differing from the original group only by its smaller size. Such a shrinking of the generic group of chemical compounds was not objectionable under Art. 123(2) EPC 1973, since these deletions did not lead to a particular combination of specific meanings of the respective residues which was not disclosed originally or, in other words, did not generate another invention. See also T 948/02, which refers in detail to this case law and which did not allow the amendment of a generic chemical formula. For another decision distinguishing its case from T 615/95, see T 1150/15; see also T 894/05, T 888/08).
In T 50/97 the board explained that in the case at issue the shrinking of the lists of alternative definitions disclosed in the application as filed was not objectionable as that limitation did not result in singling out a particular combination of specific definitions, i.e. a hitherto not specifically mentioned sub-class of compounds, but maintained the remaining subject-matter of claim 1 as generic lists of alternative definitions differing from the original lists only by their smaller size (with reference to T 615/95 and T 859/94).
In T 942/98 the board held that, through the deletion of all other meanings, residues X1, X2 and R5 had been narrowed down to a single meaning, leading to a combination of specific meanings of residues not disclosed in the application as filed. Consequently, claim 1 as filed did not in itself provide adequate support for claim 1 as amended (cited by T 2013/08 in connection with the established case law concerning "singling out").
In T 1506/13 the board, referring to T 948/02, summarised that a deletion of genes from a list of specific genes was allowable if it fulfils two conditions: First, the deletion must not result in singling out any hitherto not specifically mentioned individual compound or group of compounds, but maintains the remaining subject-matter as a generic group of compounds differing from the original group only by its smaller size. Second, the deletion does not lead to a particular combination of a specific meaning which was not disclosed originally, i.e. it does not generate another invention, or in other words it merely restricts the required protection but does not provide any technical contribution to the originally disclosed subject-matter.
In T 98/09, which concerned the "singling out" of combinations of active ingredients not originally disclosed from lists, the board held that, contrary to the appellant's view, a deletion from a list could also constitute an inadmissible extension if the singling out of one individual ingredient led to a selection of combinations which, even if conceivably covered by the application as filed, had not been specifically disclosed. It was the boards' settled case law that such a selection is to be regarded as an inadmissible extension and so as an infringement of Art. 123(2) EPC (see e.g. T 727/00 and T 686/99). The case at issue concerned two lists (six elements and 47 elements). The applicant sought to individualise one of the lists to one element. The board held that this selection was contrary to Art. 123(2) EPC. For a similar case, in which the board found that the deletion of elements of two lists led to an unallowable selection, see T 1808/08.
In T 10/97 not all the compounds listed in the original claim were included in amended claim 1. However, since the claimed group of compounds was obtained not by restricting an originally disclosed generic definition of a substituent in a generic formula to a specific one selected from worked examples, but by deleting some members from a list of individualised equally useful compounds in order to improve the chances of patentability over the available prior art, the board found that such deletions must be considered admissible in accordance with the case law of the boards of appeal (see T 393/91). For the remaining compounds, no particular technical effect was either disclosed or alleged.
In T 783/09 the board referred to T 10/97. All forty-four combinations resulting from the combination of the elements of the two lists (one list with two elements, the other list with 22 elements) were directly and unambiguously disclosed. However, a further issue was whether or not the claiming of only three of the forty-four combinations disclosed extended the content of the application as filed in an unallowable way. The forty-four combinations were referred to as "very preferred embodiments"; by this statement the skilled person was taught that each of the forty-four combinations had the same quality, i.e. they were all very preferred combinations in the context of the invention. Nothing else was derivable from the remainder of the application, i.e. a particular quality, for example a particular technical effect, was attributed neither to the three combinations of claim 1 nor to the remaining forty-one. Hence, the group of combinations in claim 1 could not be considered as the result of a selection of three qualitatively equal elements from a list of forty-four qualitatively non-equal elements – for which selection there would be no hint in the application as filed and the claiming of which group therefore would have to be considered as adding matter. Rather the group of claim 1 was to be considered as the result of the deletion of forty-one elements from a list of forty-four qualitatively equal elements (see T 10/97). In summary, the subject-matter of claim 1 complied with the requirements of Art. 123(2) EPC.
In T 2273/09 the appellants argued that the same reasoning and conclusion of T 783/09 applied to the case at issue, which related to the deletion of ten of sixteen directly and unambiguously disclosed individual combinations, with six combinations then remaining. The board referred to G 2/10 where it was held that whether the skilled person was presented with new information depended on how he or she would understand the amended claim. Applying the technical assessment of the case under consideration with regard to the remaining subject-matter claimed, the board held that the subject-matter of the main request under consideration did not meet the requirements of Art. 123(2) EPC.
In T 1075/12 the patent proprietor restricted the definitions of groups to lists of specific substituents. The board held that the more precise definitions of the groups did not result in a particular combination of specific meanings of the respective groups being singled out, namely no particular structural feature of the compounds concerned was now claimed which was not disclosed originally. The board distinguished its case from T 859/04 and T 801/02, in which more than one variable in the respective chemical formulae had been individualised, leading to a particular combination of specific meanings of the respective residues, i.e. to a particular structural feature of the compounds concerned which was not originally disclosed.